What is respirable crystalline silica and how does it impact workplace health and safety?
What Is Silica?
Silica is by far the most abundant mineral on the planet, making up around 26% of the Earth’s crust by weight.
Most of us interact with silica on a daily basis, but we often don’t even know it. Its most frequent form is quartz, which we encounter in sand, quartzite, and sandstone, among others.
Like most minerals, silica crystallizes. That means its atoms are arranged in a highly ordered, repetitive microscopic structure, forming a crystal lattice that extends in all directions. When talking about silica in the workplace, we talk about crystalline silica.
(There is another form of silica, amorphous, but this is not the subject of this Q&A.)
Respirable Crystalline Silica
Respirable crystalline silica results from the process of mechanically breaking down the naturally occurring crystalline silica into parts 100 times smaller than a grain of sand. This happens when we process sand, quartz, sandstone or other minerals and rocks that contain silica.
Why Is It Dangerous?
Silica is a hard mineral and doesn’t break easily. Under normal conditions it is not fine enough to become airborne and be inhaled.
But cutting, breaking, crushing, drilling, grinding, or blasting concrete or stone creates respirable crystalline silica. Other activities releasing silica dust are:
- Chipping, sawing, hammering
- Loading, hauling, or dumping
- Building demolition
- Facade renovation, including tuck-point work
- Abrasive or hydro blasting
- Dry sweeping or pressurized air blowing
- Tunneling, excavating, or earth moving
If we inhale the dust the silica enters and settles in the lungs. Silica damages the lung and creates scar tissue. This can lead to silicosis, an irreversible and sometimes lethal lung disease, as well as to lung cancer. There are studies showing a direct connection between repeated exposure to silica dust and lung cancer, especially for quarry, granite, brick, refractory ceramic, pottery and certain earth industries workers (read about Indoor Air Quality: The Invisible Hazard in Every Workplace).
It is possible to develop silicosis and the worker not to be aware, or to show any symptoms, at first; but in time the worker will experience shortness of breath, coughing, and body weakness. The symptoms become more and more severe with the passing of time and can lead to death.
Silicosis and lung cancer take time to develop. One single exposure is not likely to lead to these conditions. However, we can look to crystalline silica as we generally look to a sensitizer: once a specific threshold has been reached the condition sets. Many jobs in the construction, oil and gas, manufacturing, and agricultural industries are repetitive in nature and constantly expose the employee to crystalline silica, therefore potentially laying the foundation for them to develop these serious and often fatal diseases (learn about The Top 4 Pathways for Chemical Exposure).
Between 1999 to 2015, at least 55 young adults (age 15 to 44) have died from lung conditions developed due to exposure to respirable crystalline silica dust. The number of older adults is even higher and is bound to increase. This is not necessarily due to increased exposure, but because now we have better records and diagnostics.
Respirable crystalline silica is common in many industries and allowing our employees to work in an environment with high concentrations of respirable crystalline silica without protection can lead to serious disease or even death. As an employer, we have an obligation to assess the hazards of all work performed by our employees and implement controls to ensure they are protected.
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